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The 2018 Census iwi data failure and the 2023 repair

Stats NZ did not publish official statistical counts of iwi from the 2018 Census because the iwi-affiliation information was not of sufficient quality. The 2023 Census provides the next official iwi-affiliation point after 2013 and uses a different publication relationship with Te Kāhui Raraunga and Te Whata.

This is included in a GIS knowledge base because iwi statistics are frequently mapped. A polished choropleth cannot repair source data that do not support the question.

Who this example helps​

This case is particularly useful for:

  • iwi planners using demographic data
  • GIS analysts building population maps
  • researchers comparing 2013, 2018 and 2023 data
  • public-sector analysts producing iwi-level outputs

For the current iwi-oriented platform, see Te Whata in the Māori GIS projects library.

What failed in 2018​

Stats NZ's 2023 Census documentation states that official statistical counts of iwi were not released from the 2018 Census. That leaves a gap in a simple official iwi-affiliation time series between 2013 and 2023.

For GIS, the consequence is straightforward: a missing national dataset cannot safely be reconstructed by making a map look complete.

What changed in 2023​

The 2023 Census used improved approaches and alternative data sources for missing or unclassified responses. Under the Mana Ōrite relationship, Te Kāhui Raraunga publishes Māori descent and iwi-affiliation information through Te Whata in partnership with Stats NZ.

The important change is not just technical imputation. It also changes how iwi-oriented data are presented and accessed.

GIS lesson​

Before mapping a statistical field, check:

  • what population/concept it measures
  • which years are comparable
  • what geography it can support
  • whether suppressed, imputed or missing information matters
  • whether the output answers the iwi question being asked

Spatial presentation does not add quality to the underlying source.

See Provenance and source checking, Government and councils and Authoritative for what?.

Fitness for Māori purposes​

A dataset can be technically valid at one scale and still be of limited value for iwi planning. The relevant test is whether the source supports the intended question and population.

That is useful beyond Census data. Environmental, cadastral and administrative datasets all need the same source-to-question check.

Sources​

Last reviewed: 26 August 2026

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